LONDON (Reuters) - The president of athletics' world governing body the IAAF has vowed to continue efforts to stop athletes switching nationality and competing under 'flags of convenience'.

Speaking ahead of the opening of the World Athletics championships in London, Sebastian Coe said that athletes needed to have a strong connection to the country they are representing, rather than looking around for nations to run for.

"We have witnessed in the last few years the changing shape of our sport which at its best is a championship-based sport (where) the best athletes competing against each other with national identity," he said on Friday.

"I can't have a situation where I've got federation presidents reporting to me that most mornings they are waking up to emails with names of athletes looking for flags of convenience."

Unlike other sports such as soccer, athletics has allowed its competitors to switch nationalities, even after they have represented one country at international level.

Several dozen athletes changed allegiance on the eve of last year's Olympic Games in Rio de Janeiro.

In February this year, the IAAF placed an immediate stop on changes of nationality by athletes and has set up a working group to come up with new rules.

Coe said although there should be some "legitimate and genuine" chances for athletes to switch, he wanted the process to be "a lot tougher".

"It can't be done on the basis that just two federations agree and an athlete suddenly appears in a completely different uniform to the one they were running in six weeks ago," he added.